April 2009

Tips for Spring Fertility Management in Forages

Doo-Hong Min
Richard Leep
Dept. of Crop and Soil Sciences

Spring can be one of the busiest and most important seasons in terms of determining this year’s plans for sustainable and profitable production. Due to increasing fertilizer prices, it is important to make plans on how to utilize fertilizer or animal manure in forage production. The best use of manure nutrients is on crops with a high nitrogen requirement, such as corn or sugar beets. If land base is limited for manure on the farm, or hay and pasture ground are in need of the nutrients, then manure may go to grass and alfalfa fields. Following are some tips for spring fertility management for both hay and pasture.

1. Prioritize the field. Since forage fields are variable in terms of soil fertility, it is important to prioritize the fields to be fertilized from chemical fertilizer or animal manure. It would be an economic loss if expensive fertilizers are placed on low productive fields such as old stands, weedy fields, and/or low soil pH fields. Prioritizing the fertilization onto the field should be based on soil test, forage yield potential, stand health, and field uses.

2. Soil sample for soil nutrient analyses. If chemical fertilizers or animal manure are being placed on hay or pasture fields without knowing the soil nutrient levels, this may increase production cost and environmental impacts. Fertilizer or manure should be applied based on soil test results. Macro- and micro-nutrients would not be utilized properly by forage plants if soil pH is not in optimal range for forages (pH 6.0 – 7.0), particularly for alfalfa (required pH is 6.5 – 7.0). Further information on soil sampling and analyses is available at http://www.css.msu.edu/SPNL-Sampling.cfm

3. Apply fertilizer or manure in split. Since spring growth can be almost two-thirds of the whole year’s production, it is optimal to fertilize the nitrogen to the needs of the grasses for both hay and pastures ranging from 40 to 50 lb N/acre at green-up. As a rule of thumb, if the vegetation in the field is more than 50% legumes, no nitrogen is required. One of the mistakes in fertilizing forages in spring time is that some producers put the whole year’s nitrogen rate on in spring rather than doing split applications. One, larger application is vulnerable to losing large amounts of nitrogen through volatilization, surface runoff, leaching and/or denitrification (nitrogen losses in anaerobic condition such as very wet or standing water conditions).

4. Utilize animal manure efficiently. It can not be emphasized enough how important it is to know the value of manure and utilize it efficiently for forage production. Dairy manure has both macro- and micro-nutrients so that if it is utilized properly, farmers can not only save chemical fertilizer costs but also build soil quality. Applying dairy manure should be based on soil and manure analyses. Avoid manure applications to forage stands that are wet to decrease the risk of smothering plants or causing plant diseases. Ideally, manure is best utilized on non-legume forages such as corn or grasses. Legume plants such as alfalfa, red clover and white clover, however, can utilize nitrogen from two sources and there is a mutual relationship happening between nitrogen fixation and manure nitrogen. If dairy manure is applied to alfalfa fields, alfalfa prefers to utilize the free nitrogen from manure first and then fixes its own nitrogen. Therefore, applying dairy manure to alfalfa is an option to increase the acreage of manure application if the corn acres do not provide sufficient land base. Apply dairy manure to older and poorer alfalfa stands, or lower fertility alfalfa fields first if possible. Do not apply more than 3,000 – 5,000 gallons of liquid or about 10 tons of solid dairy manure per acre in a single application